Preheat your oven to 375°F (190°C).
Cook the jumbo pasta shells according to package instructions until al dente.
In a large bowl, mix the ricotta, mozzarella, Parmesan, chopped pepperoni, oregano, garlic powder, and salt and pepper until well combined.
Carefully stuff each cooked shell with the cheese and pepperoni mixture, placing them in a greased baking dish.
Spread half of the marinara sauce over the bottom of the baking dish and then place the stuffed shells on top.
Pour the remaining marinara sauce over the stuffed shells, ensuring they are well covered.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.
Remove from oven and let cool for a few minutes. Garnish with fresh basil before serving.
